The crux of the matter seems to be that my partner feels he's fallen out of love with me because our relationship has been rocky the last couple years (our lives have been very stressful--deaths, failures, financial loss, etc. taking their toll); that he's become so apathetic that he just didn't care about whether it was right or wrong. He just wanted to do something for himself. There's a part of me that can understand that, but it has also completely broken my trust in him. He says he is on the fence about whether we should try to make our relationship work; whether it's worth it after how volatile it's been. (To be clear, he says he 'loves me dearly' but isn't sure he's 'in love'. anyone who has been married a long time can understand how emotions ebb and flow, and I think it's possible to fall back in love with someone.)

It sounds like he is crying out for a bit of help. The two of you have had a rough go of it and I can see how wanting something for yourself within that would make him think it would be okay. Unfortunately he has created something else for himself and that is guilt and your lack of trust. If someone were to do this to me they would be out on their ass. At least until the whole thing could be sorted. Because I think there is potential for forgiveness.

There are two things that concern me here.

One being that he did this right in front of your face! What kind of respect is that?! I would think that he made you feel like an idiot in front of all the others that were there as they had to of noticed the "air" between you.

The other is that he acted apathetically. He seems to be completely stuck/fenced in/boxed in about your relationship and where it is at. This deserves a long hard look at, possibly with a counselor, to find out what that is to him and how to work out some way of freeing him up somehow in a way that works for you too. It could be about unfinished hardship or about how you both have been dealing with your relationship... only you two could figure that out.

As for telling the woman... I wouldn't be holding back on that personally. She should of asked and he should of told her what your thoughts were on him getting together with her. While I think she is less to blame, I still don't believe it wasn't in the back of her mind as the heat of the moment arouse.

I wouldn't be surprised if she rationalized it all away at that point as it wasn't sexy to talk about. Much like some do around safe sex... it isn't sexy to talk about your partner with a person you are just about to have sex with, as it isn't sexy to talk about wearing a condom. He did wear one right? That would create a whole other issue for me!!!!